1. Field of the Invention
The present invention relates in general to a shielded electrical connector. In particular, the present invention relates to a shielded electrical connector that provides improved shielding effectiveness to the electrical signals connected therethrough. More particularly, the present invention relates to a shielded electrical connector that provides effective shielding while is easy to control the manufacturing quality and cost thereof.
2. Technical Background
Shielded electrical connectors are widely utilized in digital computing devices for providing the connection paths for a multiple of digital signals that require shielding. One category of electrical signal connectors conveying a multiple of signals at once by providing a number of the type of pin and socket match-contacting pairs is the connector commonly referred to as the D-type connectors. A D-type connector has a number of either male pins of female sockets aligned in two or three rows that are surrounded by a shielding metal plate exhibiting the shape of a character "D" when viewed from the end of the shielded connector.
In general, the shielding of such connectors has at least three purposes. First of all, the digital signals connected via the shielded connector may be required not to generate electro-magnetic interference (EMI) signals to the surrounding environment. For example, a poorly, or unshielded D-type connector conveying tens of digital signals in a house computer may generate radio-frequency EMI to the radio receiver or television set near by. Secondly, the digital signals may themselves require not to be interfered by EMI of the surrounding environment. For example, a poorly or un-shielded D-type connector found in the computer systems operating in severe environments such as in a factory having abundant sources of EMI may have the signals conveyed therein interfered- And, last of all, the connection points in the connector for each of the conveyed signals usually require tight physical shielding against dust and moist.
To better understand the disclosure of the present invention, a brief review of the conventional shielded electrical connector follows to show the technical background. FIG. 1 is an exploded perspective view of a conventional shielded electrical connector. As is seen in the drawing, the shielded D-type electrical connector is generally comprised of a shielding cover 31 made of suitable metal material, a connector body 20 that provides the connecting means for the conveyed multiple of signals, and a pair of clamp blocks 23.
The shielding cover 31 is substantially a long-shaped piece of metal plate made by, for example, press-forming or casting. An elongated opening is surrounded by the shielding wall 35 that allows for the contacting access of the multiple of connecting means when the connector is to be used by mating with the other electrical connector. Two smaller narrow and long clamp hook openings 33 are each formed at one side of the shielding wall 35. Each of the pair of clamp hook opening 33 may receive the insertion of the clamping portion of the clamp block 23 when the entire shielded electrical connector is assembled. Two screw holes 32 are each formed at the exterior sides of the clamp hook openings 33, as is seen in the drawing. These screw holes 32 may provide for the installation of screws to assist in securing the entire assembling of the electrical connector. A pair of clamp slots 36 may each be formed on the upper and lower edges of the shielding cover 31. They provide for the clamping by the connector body 20 when the entire shielded electrical connector is assembled together.
The connector body 20 also has a substantially elongated shape as is seen in the drawing. A connector head assembly 22 protrudes out of the connector body 20 which has enclosed within its generally hollow space a number of signal connecting means, for example, the contact pins 24 in this exemplified male connector. At both longitudinal ends of the connector body 20, there is formed one clamp block hole 25 for housing the clamp block 23 when the connector is assembled. To receive and contain the clamp block 23 in a fixed and secure manner, the ends of the connector body 20 formed with the clamp block hole 25 is shaped to have the stop edge 46 at the opposite end of the opening of the hole 25, a long slot 40 at the opposite side walls of the connector body 20, as well as the arc-shaped slot 42 on the upper and lower surfaces of the connector body 20. The formation of the stop edge 46, the long slot 40 and the arc-shaped slot 42 is for fixedly containing the clamp block 23 once it is installed in the clamp block hole 25 by matching the correspondingly shaped portions of the clamp block 23. At the upper and lower edges of the connector body 20, there are provided the clamping protrusions 34 that may clamp the connector body 20 to the shielding cover 31 by inserting into the corresponding clamp slots 36.
The clamp block 23 is basically a block with a clamping hook 26 made of electrically conducting material. The use of electrically conducting material allows the clamp block 23 to constitute one section of the grounding path of the shielding of the electrical connector. The main body of the clamp block 23 has a recessed opening 41 at the opposite end of the hook 26, a pair of elevated portions 46 on the top and bottom surfaces of the main body, and a threaded hole 45 formed at the end where the hook 26 extends from the main body. One positioning hole 43 is formed in each of the elevated portions 46, including the portions 46 on the top and bottom surfaces.
When the constituting components of the conventional shielded electrical connector is assembled together, each of the pair of the clamp blocks 23 is inserted into their corresponding clamp block hole 25 of the connector body 20. When either of the clamp blocks 23 is correctly inserted into the clamp block hole 25, the main body of the clamp block 23 will be entirely buried therein, with the clamping hook 26 extending out of the surface of the main body of the connector body 20. The elevated portions 46 on both the top and bottom surfaces of the clamp block 23 will be placed in the arc-shaped slot 42 of the connector body 20 in a matched manner, while the stop edges 46 of the connector body 20 will prevent the clamp block 23 from backing off. On the other hand, the elevated portions 46 also serve to restrict the movement of the clamp block 23 toward the direction of the hook 26.
Then, the shielding cover 31 may be assembled by allowing the pair of clamping hooks 26 of the clamp blocks 23 now each installed in the corresponding clamp block hole 25 of the connector body 20 to pass through the clamp hook opening 33. This is done by aligning the connector body 20 and the shielding cover 31 and joining both together. When the two are correctly combined, the connector head assembly 22 of the connector body 20 would be installed surroundedly by the shielding wall 35 of the shielding cover 31. Meanwhile, the clamping hooks 26 now extending out of the clamp block holes 25 at both sides of the head connector assembly 22 would also extend out of the corresponding clamp hook opening 33. The screw holes 32 of the shielding cover 31 would now also be aligned with the threaded hole 45 of the clamp blocks 23. This allows the for use of screws to secure the four components, namely the shielding cover 31, the connector body 20, and each of the clamp blocks 23, tightly together.
Now, the assembled shielded electrical connector may be installed to the edge of a printed circuit board 28 that has fabricated thereon the electronic circuitries to be connected to the shielding electric connector. When the shielding electrical connector is installed to the printed circuit board 28, the edge of the circuit board is slid into the open space provided by the recessed opening 41 formed at one end of the clamp block 23, as well as the open space provided by the long slot 40 formed on the sidewall of the connector body 20. If the shielded electrical connector is correctly placed in the position on the printed circuit board 28, the positioning holes 43 formed on the clamp blocks 23 at both sides of the connector itself would be aligned with the corresponding positioning holes 48 formed on the printed circuit board 28. Means such as long pins or screws may then be employed to secure the shielded electrical connector at the proper location on the printed circuit board 28.
This type of conventional shielded electrical connectors is intended to provide both the functionality of signal shielding as well as ground path establishment. When one such connector installed to the edge of a printed circuit board is connected with a corresponding male or female electrical connector similarly shielded, the static electric charge carried by the person handling the electronic system may be discharged without damaging the circuitries connected beyond the connected pins of the pair of shielded electrical connectors. The discharging electric current may be carried by the shielding covers of the connector that are properly connected to the ground path of the system. On the other hand, since the signal connector pins and sockets that are mated within the connector pair of shielded electrical connectors are properly enclosed within the shielding covers, therefore the electrical signals are well shielded away from the environmental EMI, or from generating the EMI.
This type of conventional shielded electrical connectors, however, has at least the following disadvantages. In general, in the conventional shielded electrical connectors, the establishment of the grounding path relies on the successive electrical connection between the inner surface 31' of the shielding cover 31 and the contact surface 23' of the clamp block 23. There are, however, occasions that the contact surface 23' does not come to proper contact with the inner surface 31' of the shielding cover 31 when the entire shielded electrical connector is assembled together. Most frequent reason for this missed contact along the grounding path is due to manufacturing tolerances inevitable in the making of both the connector body 20 and the clamp block 23. The only way to discard the disqualified shielded electrical connectors when they are still in the manufacturing factory is to conduct testing of the contact itself. This would incur a considerable investment of labor and time in the manufacturing process of the connectors, since a large portion would be qualified connector products.
Moreover, the use of screw to secure the assembly of the shielded electrical connector by screwing in the threaded hole 45 of the clamp block 23 also introduces another inconvenience. Different countries employ different gauge systems for screws. To fulfill the English and metric system requirements, the clamp block 23 must be manufactured in two specifications. Two sets of press molds would be required for the clamp block, which represents increased cost for the product.